Freight trains roll through the Chicago suburb of Barrington, Ill., every day, many pulling older tank cars known as DOT-111s. They're known as the "soda can" of rail cars, says village President Karen Darch, because their shells are so thin.

Many of the DOT-111s are full of heavy Canadian tar sands crude oil. Some carry ethanol. And more and more of them are loaded with light Bakken crude oil from North Dakota.

"The worry is that if there's a derailment and the car is punctured, if any of the flammable materials in it ... spills out and explodes, it will create a huge fire, as we saw last summer in Lac-Megantic," Darch says.

The center of that small town in Quebec just north of the U.S. border was incinerated in July after an unattended oil train rolled downhill and derailed. More than 60 of the DOT-111s on that train exploded into flames, killing 47 people. Since then, safety advocates have been pressuring Canadian and U.S. officials to create new safety standards for tank cars and to make the old DOT-111s more puncture-resistant.

But the regulatory authorities have not acted yet — not even after three fiery derailments of oil trains since, all in rural areas in which no one was injured. Darch believes it's only a matter of time before there is another.

"In towns like ours, it can derail blocks from a high school with 3,000 kids, right by houses, neighborhoods where people are sleeping in the middle of the night. And even with the best response, you're going to have very catastrophic results," she says.

And it's not just those living near railroad tracks who are increasingly concerned.

"The regulatory uncertainty of not having regulations to build new cars to, or not having regulations to modify the current fleet, is starting to adversely impact my industry," says Tom Simpson, president of the Railway Supply Institute, which represents rail car manufacturers.

Simpson says that since 2011, the industry has been building to a stronger standard on its own, making new tank cars more puncture-resistant. But some are recommending an even stronger standard than that — and there's some disagreement between manufacturers, oil companies and the railroads over just how robust the new standard should be.

Manufacturers are becoming frustrated, he says.

"We are willing to build new cars to a tougher standard. We are willing to modify the current fleet to a tougher standard to continue to remove the risk of moving hazardous material by rail, but we would not take that step until we are certain that the steps we do take would be approved by the federal government," Simpson says.

And that lack of momentum was the focus of a Senate subcommittee hearing on the topic last week. Republican Susan Collins of Maine tried to pin down Transportation Secretary Anthony Foxx on when the new tank car standards would be ready.

His target date, Foxx said, is "as soon as possible."

"That's a frustrating answer," Collins said.

"I understand. It's frustrating for me to give it to you," Foxx said. "But I can promise you, senator, that we are working as hard as we can to get the rule done as quickly as we can."

When pressed, Foxx says he hopes the new rule will be ready before the end of this year. But that vague response leaves industry groups, safety advocates and community leaders somewhere they don't want to be: in oil tank car limbo.